(a) Field of the Invention
The present invention relates to a gas purifying catalyst for an internal combustion engine.
(b) Description of the Related Art
Recently, studies for removing contaminant materials included in exhaust gas exhausted from internal combustion engines of vehicles or the like have been actively conducted with the goal of protecting the global environment.
Examples of contaminant materials included in exhaust gas include carbon monoxides (CO), hydrocarbons (HC), nitrogen oxides (NOx), and the like. A three way catalyst, which may simultaneously oxidize and reduce three harmful materials (e.g. carbon monoxides, hydrocarbons, and nitrogen oxides) to thereby purify the materials, is extensively used to convert the contaminant materials into harmless materials.
The three way catalyst must have high heat resistance because the catalyst needs to be operated under a high temperature environment.
Further, since the three way catalyst is used under the high temperature environment, in the case where the three way catalyst is supported on a carrier, there is a problem in that noble metals in a catalyst layer of the three way catalyst form alloys. This reduces the activity of the catalyst. FIG. 1A illustrates a current technology of using a double layer structure including a lower layer in which noble metal Pd 52 is carried in a first support 40 and an upper lower layer in which Rh 54 is carried in a second support 42. This structure is generally applied in order to prevent the problem of alloy formation. As illustrated in FIG. 1B, when the catalyst of the double layer structure is used at high temperatures, Pd and Rh exist separately in the lower layer and the upper layer, thus preventing alloying thereof.
However, the double layer structure technology has a problem in that manufacturing costs are increased. As such, a single layer catalyst technology is preferable.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.